Integrated capacitive device with hydrogen degradable dielectric layer protected by getter layer

ABSTRACT

There is described an integrated device comprising a thin-film capacitor formed of first and second electrodic layers, electrically separated by a dielectric layer formed of a hydrogen-degradable compound characterized in that it further comprises at least a getter layer of a material of the group consisting of the alloys of zirconium, vanadium and iron, optionally containing minor quantities of manganese and/or elements of the “Rare Earths” group, alloys of zirconium with at least one among the metals of the group consisting of iron, cobalt and nickel, optionally containing up to 15% by weight of elements belonging to the “Rare Earths” group.

FIELD OF THE INVENTION

[0001] The present invention relates in general to integrated circuitsand in particular to storage devices whose structure comprises adielectric layer of capacitive coupling having ferroelectric featuresand/or a high dielectric constant, both in the case that the storagedevice employs the features of residual polarization of theferroelectric oxide or the capacitive coupling through the dielectricoxide for storing an information in the form of electric charge.

TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0002] Ferroelectric and particularly dielectric compounds based onmixed oxides or equivalent compounds with ferroelectric features arematerials used in different fields and particularly in the manufactureof integrated structures on a semiconductor or dielectric substrate.Piezoelectric filters, ultrasonic transducers which employ thepiezoelectric features, infrared transducers, optical sensors employingfeatures of pyroelectricity, optical modulation devices, opticaldiaphragms based on the employment of electro-optical features are someapplications of these materials.

[0003] The possibility to manufacture extremely thin dielectric films ofmaterials having ferroelectric features has favored the development ofnonvolatile storage devices with ferroelectric capacitor which employthe stability in time of the residual polarization of the thin layer offerroelectric material of the capacitor. These devices (storage cells)have been developed by virtue of their potentiality to be manufacturedin extremely compact size so as to increase the storage capacity and thelevel of integration of the whole integrated device or their markedability to preserve the information even in particularly hardconditions. Ferroelectric dielectrics which are commonly used in themanufacturing processes of integrated devices are lead zirconatetitanate, PbZr_((1−x))Ti_((x))O₃, commonly known with the acronym PZT,bismuth and strontium tantalate or Sr₂Bi₂Ta₂O₉, commonly known with theacronym SBT or Y1 and the lanthanum and bismuth titanate, commonly knownwith the acronym BLT. These are among the most used materials formanufacturing the so-called FeRAM storage devices.

[0004] Another similar dielectric material (also with ferroelectricfeatures) used as dielectric layer, in particular as dielectricinterpoly of capacitive coupling between a control gate structure(wordline) and the floating gate of the cell in DRAM cell structures, isbarium and strontium titanate, Ba_((x))Sr_((1−x))TiO₃, also known withthe acronym BST.

[0005] The materials preferably used for exploiting the ferroelectricfeatures thereof in FeRAM are the above mentioned PZT and also the SBTor the BLT, whereas the BST is most frequently used in the DRAMs byvirtue of an increased possibility to deposit extremely thin filmsthereof having a high dielectric constant, free from defects.

[0006] The techniques of deposition of said layers of dielectriccompounds with ferroelectric features can be various, such as forexample by “sputtering”, or by chemical deposition from the vapor phase(CVD) wherein a decomposable compound, commonly an organometalliccompound of precursor metals, is deposited from the vapor phase on asuitable substrate.

[0007] Another method of formation of said layers is the so-called“sol-gel” method, wherein a solution of precursor compounds is used inorder to form a film on a substrate commonly by thermal decomposition ofseveral applications of sol-gel. There is also a method based on thecreation of a “mist” of ionized drops of the solution of a metallorganicprecursor compound, which are deposited on the wafers. Once the solventis evaporated, the metallorganic compound is decomposed at hightemperature in a strongly oxidating environment so as to form a film ofcomposite oxide. This technique is known in the literature as “LiquidSource Misted Chemical Deposition” or briefly LSMCD.

[0008] Other methods of preparation are known in the literature.

[0009] Leaving out of consideration the particular function of thethin-film capacitor of dielectric material with high dielectric constantoptionally also with marked ferroelectric features and of the relevantintegrated structure to which it belongs, whether that of a FeRAM, of aDRAM or else, the formation of the thin-film capacitor in a flow ofmanufacturing process of a common semiconductor integrated device, forexample in CMOS technology, implies a number of problems due to aprecise risk of exposition of the thin layer, generally based on oxides,to hydrogen. As a matter of fact, in a common flow of a manufacturingprocess of integrated devices, there are a number of operations whereinhydrogen is present that remains partly trapped or incorporated in thewafer during the manufacture, typically in the semiconductor siliconsubstrate.

[0010] For example in a CMOS process, the devices (transistors) definedin the active areas can be exposed to an annealing treatment in hydrogenatmosphere for neutralizing bonds which are left “dangling” in thesemiconductor in order to reduce problems of superficial charge at theinterface between the semiconductor and the gate oxide. During thisannealing treatment, hydrogen can remain trapped in the substrate whichthus become a source of hydrogen diffusion during the working life ofthe integrated device. Other sources of exposure to hydrogen can beidentified in the so-called “back-end” steps of the process, during theformation of metallizing aluminum layers, the steps of formation oftungsten plugs for the contacts and of the IDL layers, wherein theprocess conditions are such that the presence of hydrogen is implied.

[0011] Hydrogen can also be present during the sealing and encapsulatingsteps of the integrated device, in the case of ceramic “packaging”.

[0012] Also during the working life of the devices, a certain diffusionof hydrogen inside the device can take place.

[0013] The effects of degradation of a dielectric film, optionally withferroelectric features, generally formed of an oxide or more frequentlyof mixed oxides or equivalent compounds, upon exposition to hydrogen arewell-known and discussed in the literature. In particular a hydrogendegradation of the ferroelectric film of a FeRAM causes a contraction ofthe hysteresis curve, thus reducing the separation between the logicalvalues 1 and 0 on the ordinate axis, which effect can bring about adifficulty in the discrimination criteria in the reading step of theinformation stored in the ferroelectric film capacitor. In the case of aDRAM, the degradation of the thin dielectric film of interpolycapacitive coupling determines a lost of electric charge stored in thefloating gate through the wordline.

[0014] The suggestions made until now in order to overcome this criticalaspect of the dielectric and ferroelectric materials having a highdielectric constant towards a hardly avoidable hydrogen exposure havebeen several.

[0015] Document EP-A-605980 discloses a growth PECVD technique of aSi₃N₄ and SiON layer having a low hydrogen content as interdielectricstate of a FeRAM device, using TEOS (Si(OC₂H₅)₄) and N₂ instead of thecommon mixture of SiH₄/NH₃/N₂.

[0016] Patent U.S. Pat. No. 5,523,595 discloses the sputtering of a TiNor TiON layer on the FeRAM device using a PZT deposited via sol-gel,with functions of barrier-layer towards hydrogen and humidity.

[0017] Patent U.S. Pat. No. 5,481,490 discloses the deposition of a thinlayer of nitride of aluminum, silicon or titanium on the ferroelectriccapacitor in order to prevent the degradation of the ferroelectric filmof the capacitor during the annealing treatments which are foreseen inthe manufacturing process of the device, during which the gases H₂ andN₂ are used.

[0018] Patent U.S. Pat. No. 5,591,663 discloses a particular sequence ofa manufacturing process of a FeRAM device using conventional materialswhich avoids the hydrogen degradation during the annealing treatment.

[0019] Document EP-A-0837505 discloses a structure comprising aferroelectric capacitor, wherein a second layer of ferroelectricmaterial PZT is deposited on the already defined structure of theferroelectric capacitor so that said second layer of PZT acts as asacrificial layer thus preventing hydrogen from reaching and degradingthe PZT layer of the capacitor.

[0020] Document EP-A-0911871 discloses the formation of a thin layer oftantalum and silicon nitride on the ferroelectric capacitor structurewith function of barrier layer against the possible diffusion ofhydrogen towards the ferroelectric layer of the capacitor.

[0021] Patent U.S. Pat. No. 5,760,433 discloses the use of a sacrificiallayer of a material chemically reactive towards hydrogen which isarranged on the capacitor structure as a protection of the ferroelectriclayer of the capacitor. The sacrificial material can contain Sr, Nb, Taand/or Bi, bismuth oxide, palladium oxide.

[0022] Patent U.S. Pat. No. 5,716,875 discloses a FeRAM structurewherein, after annealing in N₂+H₂, a layer of silicon nitride Si₃N₄ isdeposited on the integrated structure of the transistor and on the backof the substrate wafer for encapsulating (isolating) the structure andpreventing in the future the possible effects due to hydrogen retentionafter the annealing treatment. On a structure so “isolated” with regardsto the diffusion of the hydrogen therein sorbed, there is formed theferroelectric capacitor, which can be therefore advantageously annealedin oxygen atmosphere without causing degradation of the transistorfeatures. On the other hand the hydrogen possibly trapped in the so“insulated” wafer structure will be not able to reach and to degrade theferroelectric film of the capacitor thanks to the barrier offered by thenitride layer.

[0023] Document EP-A-0951059 discloses a particular manufacturingprocess wherein a final annealing in oxygen would solve the hydrogendegradation which could have taken place during the metallizationprocesses.

[0024] Patent U.S. Pat. No. 5,990,513 describes the formation of aninterlevel dielectric layer with hydrophilic properties covered by adielectric layer having reduced hydrophilic properties for protectingthe ferroelectric layer during the annealing treatment in hydrogenatmosphere in the case of a ceramic encapsulated device. Ceramicencapsulation requires generally an annealing process at 440° C.

[0025] Document JP-11293089 describes the formulation of an epoxydicresin usable for encapsulating a FeRAM device having features of lowhydrogen release at 175° C. for 90 minutes.

[0026] Document JP-11187633 discloses the use in a FeRAM device of ametal layer formed of a material capable to store hydrogen during themanufacturing steps. Then, the sorbed hydrogen is expelled by means ofthermal treatment under vacuum. The used material can be Pd, V, Ni, Nb,Ti, Fe, Mg, TiFeLaNi₂, Ti₂Mn₃ VNb, TiCo, ZrMn₂, Mg₂Cu, Mg₂Ni, LaCo₃,Ti₂V₈, Ti₂C, Ti₂Fe, Ti₂CoMn.

[0027] Document JP-1140761 discloses the use of a layer of Ta or V or Nbdeposited on the ferroelectric capacitor for protecting the latter fromhydrogen degradation.

[0028] Document JP-118355 discloses the use of a hydrogen barrier layerformed of titanium dioxide or silicon nitride arranged under the lowerelectrode of the ferroelectric capacitor and of a barrier layer arrangedover the upper electrode of the ferroelectric capacitor of the samematerials or alternatively of titanium nitride or of TiOSi.

[0029] Document JP-2000-40799 discloses that, by making a reactive layerof Pb—Pt—Ti—O between the PZT ferroelectric layer and the Pt upperelectrode of a ferroelectric capacitor, it is possible to prevent thediffusion of hydrogen towards the dielectric and often ferroelectricfilm of the capacitor.

[0030] Until today, the most commonly followed approach is interposing abarrier layer towards the diffusion of hydrogen as a protection of thepreformed structure of the thin-film capacitor. Obviously, said barrierlayer is effective only towards the hydrogen coming “from above”, thatis, the hydrogen which is present in the back-end steps of themanufacturing process of the integrated device. However, said barrierlayer is not effective against a possible diffusion of hydrogen “frombelow”, that is, from the hydrogen which has been trapped in the waferduring the annealing treatment in hydrogen of the active structures,which have been formed before making the capacitor. Some known solutionsimply the formation of a barrier layer towards the diffusion of hydrogeneven under the lower electrode of the thin-layer capacitor.

[0031] In most of the suggested solutions the approach is anywayprotecting the thin layer of dielectric and/or ferroelectric material ofthe capacitor by means of barrier layers which insulate it towards apossible hydrogen diffusion.

[0032] The barrier layers tend to stop hydrogen diffusion towards theelectrodes and therefore towards the dielectric and/or ferroelectric orhaving a high dielectric constant material in a passive way. In the casefor example of oxides, in addition to the passive effect there is alsothe chemical reaction between hydrogen and oxide which produces water.This reaction eliminates hydrogen, producing the hydrogen compound.

[0033] Also the materials disclosed in the further document JP-11187633for retaining hydrogen which is then removed by thermally treating undervacuum the device before the final encapsulation thereof are capable tosorb hydrogen in a significative way only at atmospheric pressure.

OBJECT AND SUMMARY OF THE INVENTION

[0034] The main object of the present invention is providing a thin-filmcapacitor structure, wherein the dielectric is formed of a materialhaving high dielectric constant and optionally having also ferroelectricfeatures, protected from the risk of degradation of the dielectricmaterial due to hydrogen diffusion in a more effective way than it isobtainable with the known techniques and without the above mentioneddrawbacks and limitations.

[0035] This important result is obtained by providing, under the lowerelectrode and over the upper electrode of the thin-film capacitor, alayer of getter material which is capable of sorbing and retaininghydrogen even at sub-atmospheric pressures without giving rise tochemical bonds (reacting) with hydrogen and/or to morphologicalmodifications of the material.

[0036] The sorbing action exerted towards hydrogen by the gettermaterial, in addition to sequestering the hydrogen remained in thefinished device, retains it thus avoiding that it can degrade thedielectric-ferroelectric film, without giving rise to generation ofwater and without chemically reacting with hydrogen.

[0037] However, in order to obtain this result it is necessary that thegetter material has hydrogen equilibrium pressures lower than 1 mbar atthe room temperature and that the thickness sufficient for retaining thepresent hydrogen is compatible with the stringent requirements ofcompactness of the integrated structures. Basically, the getter materialis an alloy made of zirconium, vanadium and iron, optionally containingminor quantities of manganese and elements of the group of the “RareEarths”, or an alloy of zirconium and at least one of the metals of thegroup consisting of iron, cobalt, nickel and optionally containing up to15% by weight of “Rare Earths”.

[0038] One layer of getter material is deposited over the layer ofmaterial forming the upper electrode of the capacitor and, morepreferably, also under the layer forming the lower electrode of thethin-film capacitor, optionally deposited on a first layer of adhesion,for example titanium, interposed between the laminated structure of thecapacitor and the support layer.

[0039] The getter layer provided under the lower electrode of thethin-film capacitor intercepts the hydrogen which may diffuse from thesubstrate if it has been sorbed by the substrate during a previous stepof annealing in hydrogen of the wafer. Typically said lower getter layercan have a lower thickness (of the order of 50-100 nm) than the uppergetter layer which can have a thickness also up to about 200 nm.

[0040] The lower getter layer can effectively contribute to sensiblyincrease also the adhesion between an electrodic layer, for example of anoble metal or alloy of a noble metal, and the underlying support layer,often in FeRAM or DRAM device, an amorphous layer of silicon oxide dopedwith boron and phosphorous (BPSG). In many cases, it can provide thenecessary adhesion, thus avoiding the need to interpose a specificadhesion layer with the support layer.

[0041] The getter layer which is provided over the upper electrode ofthe ferroelectric capacitor intercepts and traps the hydrogen which candiffuse through the insulating, metallizing and passivating layers,commonly placed over the defined structure of the ferroelectricthin-film capacitor during the subsequent steps of the fabricationprocess of the integrated device, included in some cases also theencapsulating steps of the device (packaging).

[0042] Both the getter layer formed over the upper electrode of thecapacitor and the getter layer optionally formed under (depositedbefore) the lower electrode of the capacitor can be defined throughappropriated masking and attacking steps together with other layers ofthe structure. In particular the upper getter layer can result to beself-aligned to the perimeter of definition of the capacitor.

[0043] Alternatively, the getter layer can be defined through a suitablemasking step, also with a wider perimeter than the perimeter of thecapacitive coupling area.

[0044] The invention is clearly defined in the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0045]FIG. 1 is a schematical cross-section of a structure of athin-film capacitor according to the invention.

[0046]FIG. 2 is a schematical cross-section of a FeRAM storage cell madeaccording to the present invention.

[0047]FIG. 3 is a schematical cross-section of a DRAM storage memory,made according to the present invention.

[0048]FIG. 4 shows hydrogen sorption features of two different materialsof the invention as a function of the quantity of sorbed gas, at theroom temperature as well as the corresponding curves measured on threebarrier materials according to the known art and on the pure metalszirconium and titanium.

DESCRIPTION OF SOME PREFERRED EMBODIMENTS OF THE INVENTION

[0049]FIG. 1 shows in a schematic way the cross-section of a thin-filmcapacitor structure with dielectric layer 1 of an oxide having a highdielectric constant and ferroelectric features comprising an uppergetter material layer and a lower getter material layer, made accordingto the present invention.

[0050] Dielectric layer 1 having ferroelectric properties of thecapacitor can be of a material of the group formed of PZT, SBT, BST, BLTas above described, or equivalent.

[0051] The material forming both upper 3 and lower 2 electrodes of theferroelectric capacitor, can be a material of the group formed ofplatinum, iridium, rhodium, ruthenium, silver or gold; alloys of thesame metals with themselves or with other non-noble metals; conductiveoxides containing at least one noble metal oxide or lead, mixed oxidesof a noble metal and a metal such as titanium, tantalum, zirconium andmixtures of the same metals; polysilicon and polysilicon doped withboron, phosphorous or arsenic; and equivalent electrically conductivematerials.

[0052] Lower getter layer 4 and upper getter layer 5 are made of amaterial of the group consisting of the alloys of zirconium, vanadiumand iron, optionally containing minor quantities of manganese and/orelements of the “Rare Earths” group, alloys of zirconium with at leastone of the metals of the group consisting of iron, cobalt, nickel andoptionally containing up to 15% by weight of elements of the group ofthe “Rare Earths”.

[0053] In particular, alloys based on zirconium, vanadium or iron areexceptionally effective in sorbing and trapping hydrogen, even atsub-atmospheric pressures, such as those which are normally presentduring crucial treatment steps in the presence of hydrogen of the commonCMOS manufacturing processes.

[0054] Another feature of the above mentioned alloys is a highercapacity of retaining hydrogen at relatively high temperature, whenother types of metal materials would show a marked release of the sorbedhydrogen.

[0055] A possible sequence of a process for manufacturing themulti-layer of FIG. 1 comprises:

[0056] forming an insulating support layer of the capacitor;

[0057] depositing getter material 4 by any technique selected among thephysical deposition techniques such as sputtering, laser ablation,cathodic arch and evaporation, or chemical deposition techniques such asMOCVD or LSMCD by starting in the two latter cases from a metallorganicprecursor compound containing the getter metal or metals;

[0058] depositing the material of lower electrode 2 by sputtering;

[0059] depositing the dielectric material optionally with ferroelectricfeatures or high dielectric constant, by means of sputtering or sol-gelor MOCVD or LSMCD, starting in the two latter cases from metallorganicprecursor compounds containing the metal or the metals of theferroelectric material;

[0060] depositing the material of the upper electrode 3 by sputtering;

[0061] depositing getter material 5, by any technique selected among thephysical deposition techniques such as sputtering, laser ablation,cathodic arch and evaporation, or chemical deposition techniques such asMOCVD or :LSMCD by starting in the two latter cases from a metallorganicprecursor compound containing the getter metal or metals.

[0062] The thickness of the dielectric layer 1 of ferroelectric or highdielectric constant material is generally of the order of or lower than200 nm, while the total thickness of the two layers 2-4 and 3-5 ofelectrodic material and getter material is also generally lower than 200nm. The layers of getter material 4 and 5 can have a thickness of about150 nm. The lower getter layer 4 can have a reduced thickness withrespect to the upper layer 5.

[0063] The definition of the thin-film capacitor and of the getter layeror layers can be carried out according to the common masking andattacking techniques. In particular, while the lower getter layer 4 canbe defined together to the lower electrode, on which can be necessary toestablish a contact or a way of interconnection, the upper getter layer5 can be defined together with the upper electrode layer 3 and thedielectric layer 1 of the capacitor by means of a single masking andattacking step. Alternatively, the upper layer of getter material 5,deposited on a predefined structure of a capacitor can be in its turndefined by means of a masking and attacking step also with a widerperimeter than the perimeter of the underlying capacitor structure.

[0064]FIG. 2 is a classical representation of the cross-section of aFeRAM storage cell, the ferroelectric capacitor of which it is madeaccording to the present invention.

[0065] The support layer 7 on which the ferroelectric thin-filmcapacitor structure is formed is typically an insulating dielectriclayer 7 of the structure of the MOS transistor, indicated as a wholewith 8 in the figure, made in the active area defined by the field oxide9 grown on the semiconductor substrate 10.

[0066] Support layer 7 is commonly formed of silicon oxide (for examplea glass doped with boron and phosphorous deposited by chemicaldeposition from the vapor phase).

[0067] On support layer 7 is deposited the bottom getter material 4 andsubsequently a layer 2 of an electrodic material, which are defined by afirst masking and attacking step.

[0068] Then, the material of the dielectric and ferroelectric film 1 isdeposited, followed by the deposition of the upper electrodic layer 3and of the upper getter layer 5.

[0069] The so formed stack is then defined by means of a further maskingand attacking step, thus defining the thin-film capacitor between thetwo getter layers 4 and 5 of protection of the possible hydrogendiffusion towards the layer 1.

[0070] When the definition of the structure of the ferroelectriccapacitor is completed, a second insulating layer 11 is commonlydeposited, through which the upper portions of the contacts of thetransistors and the interconnection ways 12 and 13 of the ferroelectricthin-film capacitor associated with the transistor, respectively on thelower getter layer 5 and on the lower electrodic layer 2.

[0071] Then, the first level metallization layer (metal 1), which issubsequently defined by masking and attacking is deposited.

[0072] The cross-section illustrated in FIG. 2 shows also the carriedout deposition of a third insulating layer 14.

[0073] Because of the exceptional dielectric features and of thepossibility of being formed (deposited) in the form of films having athickness which may be even extremely reduced (≦10 nm) lacking ofdefects, similar dielectric materials sensible to degradation phenomenain the presence of hydrogen are commonly used also for applicationswherein their high dielectric constant is used, independently on theiroptional ferroelectric feature which may be more or less marked.

[0074] A typical field of use of these materials is for forming theinterpoly dielectric thin film which separates the two levels ofpolysilicon (poly) thus forming the storing capacitor of information inthe form of electric charge of a DRAM storage cell.

[0075] According to the most recent techniques, the DRAM cells canmaintain a classical configuration of the “stack” type, that is with thethin-film capacitor formed on the semiconductor substrate or of the“trench” type, wherein the structure is partially made in a previouslyproduced groove of the semiconductor substrate.

[0076]FIG. 3 shows a modern DRAM structure wherein the storing capacitorof the electric charge is made by capacitive coupling through a thindielectric film 1 interposed between electrodes 2 and 3 respectivelydefined in poly 3 and poly 2.

[0077] For protection of the so formed structure from a possiblehydrogen diffusion present in a number of subsequent steps of themanufacturing process of the storage device, over the upper electrodiclayer 2 defined of poly 3 is deposited a getter layer 5 according to theinvention which, by encapsulating completely the structure of the DRAMcapacitor, protects from a possible degradation of the dielectricfeatures of the thin-film 1 of capacitive coupling, capturing andblocking hydrogen and preventing it form reaching and going through theconductive electrode layer 2 of poly 3 and thus reaching the thindielectric layer 1 of capacitive coupling.

[0078] The getter layer 1 can have a thickness between 20 and 100 nm.

[0079] The features of dynamic sorption of the hydrogen of the twopreferred getter materials used for forming the layers of protectionfrom hydrogen of the invention (curves 1 and 2) are compared in FIG. 4with those of pure metals such as zirconium and titanium (curves 3 and4) and with those of barrier materials (curves 5, 6 and 7) described inthe above mentioned previous documents.

[0080] The composition relating to curve 1 comprises a 3% of MM. By theterm MM is shortly indicated the so-called “misch metal” material whichis a mixture of rare earths of variable composition.

[0081] As it can be easily noted, the getter layers according to theinvention which intercept and block the hydrogen have, differently formthe known materials, a dynamic sorption capacity and a volumetricsorption capacity which are compatible with stringent requirement ofcompactness and more particularly of maximum tolerable thickness valuesof the most advanced manufacturing processes of the storage devices.

1. An integrated device comprising a thin-film capacitor formed of firstand second electrodic layers, electrically separated by one dielectriclayer consisting of a hydrogen-degradable compound, the integratedstructure comprising optionally a metal layer of adhesion between asupport and the lower electrodic layer of the capacitor, a protectivelayer above the upper electrodic layer of the capacitor and anintermediate dielectric layer covering the structure of the capacitor,characterized in that it comprises a getter layer of a material of thegroup consisting of alloys of zirconium, vanadium and iron, optionallycontaining minor quantities of manganese and/or elements of the “RareEarths” group, alloys of zirconium with at least one among the metals ofthe group consisting of iron, cobalt and nickel, optionally containingup to 15% by weight of elements of the “Rare Earths” group.
 2. A deviceaccording to claim 1, characterized in that it comprises a second getterlayer on the upper face of said support.
 3. A device according to claims1 or 2, wherein said electrodic layers of the capacitor are of amaterial belonging to the group consisting of platinum, iridium,rhodium, ruthenium, silver or gold, alloys of the same metals,conductive oxides of iridium, rhodium, ruthenium and lead,non-stoichiometric mixed oxides of iridium and/or ruthenium and/orrhodium and of at least another metal of the group consisting of Ti, Taand Zr and mixtures of the same metals, polysilicon and polysilicondoped with boron, phosphorous or arsenic.
 4. A device according to claim2, wherein said second getter layer also acts as an adhesion layerbetween said support and the lower electrodic layer.
 5. A deviceaccording to claim 1, wherein the thickness of said getter layer is nothigher than 200 nm.
 6. A device according to claim 2, wherein thethickness of said second getter layer is not higher than 100 nm.
 7. Aferroelectric storage device comprising a semiconductor substrate, a MOStransistor formed in said substrate, and at least one ferroelectricthin-film capacitor functionally connected to a current terminal of saidMOS transistor, formed above at least one first insulating layer of theintegrated structure of said MOS transistor, said capacitor being formedof a first lower electrodic layer, of a ferroelectric oxide layer and ofa upper electrodic layer, characterized in that over the upperelectrodic layer of the ferroelectric capacitor is provided a getterlayer of a material of the group consisting of alloys of zirconium,vanadium and iron, optionally containing minor quantities of manganeseand/or elements of the “Rare Earths” group, alloys of zirconium with atleast one among the metals of the group consisting of iron, cobalt andnickel, optionally, containing up to 15% by weight of elements of the“Rare Earths” group.
 8. A device according to claim 7, characterized inthat it comprises a second getter layer on the upper face of said firstinsulating layer.
 9. A device according to claim 7 or 8, wherein saidelectrodic layers of the capacitor are of a material of the groupconsisting of platinum, iridium, rhodium, ruthenium, silver or gold,alloys of the same metals, conductive oxides of iridium, rhodium,ruthenium and lead, non-stoichiometric mixed oxides of iridium and/orruthenium and/or rhodium and of at least another metal of the groupconsisting of Ti, Ta and Zr and mixtures of the same materials.
 10. Adevice according to claim 8, wherein said second getter layer also actsas an adhesion layer between said first insulating layer and the lowerelectrodic layer.
 11. A device according to claim 7, wherein thethickness of said getter layer is not higher than 200 nm.
 12. The deviceaccording to claim 8, wherein the thickness of said second getter layeris not higher than 100 nm.
 13. A DRAM device comprising a semiconductivesubstrate, a MOS transistor formed in said substrate and a thin-filmcapacitor for storing the information in the form of electric chargeassociated to said transistor and consisting of electrodes made ofpolysilicon of two subsequent levels and coupled through a dielectricfilm, characterized in that over at least the area of capacitivecoupling of said electrodes of polysilicon is provided a getter layer ofa material of the group consisting of alloys of zirconium, vanadium andiron, optionally containing minor quantities of manganese and/orelements of the “Rare Earths” group, alloys of zirconium with at leastone among the metals of the group consisting of iron, cobalt an nickel,optionally containing up to 15% by weight of elements of the “RareEarths”group.